This invention relates to a process for forming an image comprising imagewise exposing a photosensitive material comprising a compound which reacts with a photosensitive silver halide upon heating to form or release a mobile dye, and transferring the resulting mobile dye to a dye-fixing element in the presence of a hydrophilic solvent.
A number of methods have been proposed for producing color images through heat development. Among others, U.S. Pat. Nos. 3,531,286; 3,761,270; and 4,021,240; Belgian Pat. No. 802,519; and Research Disclosure, September 1975, pages 31-32, disclose a process for forming a color image through coupling of an oxidant of a developing agent with a coupler, and a variety of developing agent used therein.
Research Disclosure, May 1978, pages 54-58, RD-16966 describes a process of forming an image by incorporating a nitrogen-containing heterocyclic group into a dye to form a silver salt and effecting heat development to release the dye.
A process for forming a positive color image by heat-sensitive silver dye bleaching process is also well known. Useful dye bleaching processes are disclosed in, for example, Research Disclosure, April 1976, pages 30-32, RD-14433; ibid, December 1976, pages 14-15, RD-15227; and U.S. Pat. No. 4,235,957.
A process for forming a color image using a leuco dye is described in, for example, U.S. Pat. Nos. 3,985,565 and 4,022,617.
These color image forming processes, however, have the drawback that during an extended period of storage, discoloration of color images formed and coloration of white areas occur under the action of coexisting silver halide, silver complex, developing agent and the like. New color image forming processes by heat development which are substantially free of such drawbacks are described in Japanese Patent Application Kokai Nos. 57-179840, 57-186774, 57-198458, 57-207250, 58-58543, 58-79247, 58-116537, 58-149046, 59-48764, 59-65839, 59-71046, 59-87450, 59-88730, etc. These processes are designed such that a mobile dye is formed or released in proportion or counter-proportion to the reduction of photosensitive silver halide into silver by heat development, and the resultant mobile dye is transferred to a dye-fixing element.
For the spectral sensitization of silver halide with a sensitizing dye in these processes, cyanine and merocyanine dyes are believed advantageous because of their high sensitivity. Some of these dyes can contaminate an image on the dye-fixing element, particularly white areas thereof. There is a continuing need for improvement in this respect.